Isomerization of paraffins



Patented Dec. 24, 1940 ISOMERIZATION or PARAFFINS Aristid V. Grosse,Bronxville, N. Y., and Herman Pines, Chicago, Ill., assignors toUniversal Oil Products Company, Chicago, 111., a corporation of DelawareNo Drawing. Application January 17, 1940, Serial No. 314,282

. not available for the neo-pentane. Similarly, the i 4 Claims.

This application is a continuation-in-part of our co-pending applicationSerial No. 118,587, filed December 31,1936.

This invention relates particularly to the isomerization of straightchain parafiin hydrocarbons which are normally liquid. I

In a more specific sense the invention is applicable not only toindividual paraflin hydrocaricons of normal straight chain structure butalso to hydrocarbon mixtures containing these compounds in substantialpercentages such as straight run gasolines and their fractions, whichcontain I in addition to paraflin hydrocarbons of highly knockingcharacteristics other hydrocarbons comprising some paraffins of branchedchain structure and the usual run of naphthenes and aromatics. Theisomerization of individual paraffin hydrocarbons such as n-pentane orn-hexane is frequently desirable in the manufacture of derivatives sincethe'isomeric compounds are more reactive and, in the case of gasoline orgasoline fractions, the isomerization has the efiect of increasing theantiknock value of the gasolines to a marked extent as will be shown inlater examples.

There is no need for extensively recounting the number of possibleisomers of parafiln hydrocarbons since these are all predictable on thepresent theories of organic chemistry and are well known to thosefamiliar with this subject. However, the following table is shown toindicate in a general way the change in structure and properties ofnormal paraflin hydrocarbons and their isomers, particularly since the'pentanes constitute some of the lower-boiling constituents of ordinarygasolines.

Boil- Octan Compound Formula inn Density numpoint ber n-PentaneCHa(CH2)aCHa 36.3 o.s475 o c 63 CH:\ i-Pentarm tenement 2s o.sa94@o 88CH2 v Neo-pen- C(CHS) 9.5 O.6251@l4.4 C..

ta'ne while the antiknock value asexpressed by octane number generallyincreasesalthough figures are hydrocarbons'in gasolines, thedetermination of 1 erately superatmospheric pressures and varying PATENTOFFICE isomeric hexanes, heptanes, and octanes will show the sameprogressive relationships as their structure becomes more condensed. Asthe molecular weight of paraflin hydrocarbons increases, the number ofpossible and known isomers increases more than arithmetically so that incase of isomerizatlon involving mixtures oin-paraflins and particularlyn-parafiins in admixture with other the extent of isomerization is notpossible by analytical methods but can be estimated from the observedchange in antiknock value.

In one specific embodiment the present invention comprises treatment ofn-paraifin hydrocar- 16 locus or hydrocarbon mixtures containingsubstantial percentages thereof such as straight run gasoline fractionswith catalysts comprising zirconium chloride and hydrogen chloride toeffect isomerization reactions. 20

Zirconium chloride is a white crystalline solid which sublimesfat 300 C.and has been found to be efiective in promoting isomerization ofnormally liquid normal paraffin hydrocarbons into substantialpercentages of isomeric compounds of 25 more highly branched structureand also of increased degree of branching in hydrocarbons which may havesome side chains but not the maximum possible number. It has furtherbeen found that this isomerization which is of particu- 30 lar benefitin the treatment of straight run gasolines to improve their antiknockvalue is best conducted in the presence of small but necessaryproportions of hydrogen chloride. The temperature, pressure, and timesof contact necessary for ef- 35 fecting an optimum amount ofisomerization will obviously vary with each compound or mixture ofcompounds treated so that only broad ranges of these factors can begiven. In general, temperatures of 0-300 0., normal atmospheric ormodtimes of contact may be employeddepending upon .whether theoperations are conducted in batch or continuous types of plants. In anycase there will be an optimum setof conditions at which maximumisomerization reactions are effected with minimum decompositionsinvolving the breaking of carbon-to-carbon bonds and the formation ofhydrocarbons of lower and higher molecular weight than the originalmaterial treated.

The present process may be operated under batch or continuous conditionsand either in liquid, mixed or vapor-phase as may be desirable orexpedient in view of the particular hydrocarbon or hydrocarbon mixtureundergoing treatment. A

imple method of operation consists in adding o per cent of granularanhydrous zirconium hloride to a treating vessel containing hydrocarnsand provided with a mechanical agitating device of some description. Itis best to employ a treater which can besealed from atmospheric contactand which can be operated under superatmospheric pressure. Thesoligicatalyst is then kept in suspension by moderate agitation whileintroducing a slow stream of hydrogen chloride.

In another type of operation which accelerates the rate ofisomerization, the hydrocarbon mixture may be kept at its boiling pointby moderate heating under reflux conditions with the granular chloridemaintained in suspension by the ebullition, while the hydrogen halide isagain added in a slow stream. In this type of operation any desiredsuperatmospheric' pressure may be employed to permit the use of anydesired temperature; The necessary amount of hydrogen chloride may begenerated by adding a small amount of water or steam which causes anequivalent amount of hydrolysis.= Vapor-phase operations may beconducted by passing vapors of hydrocarbons mixed with a small amount ofhydrogen chloride over solid granular catalysts comprising the zirconiumchloride. pound may also be vaporized in a stream of inert gas andinjected into a slow stream of the vapors of a hydrocarbon undergoingisomerization after which the spent or partly spent catalyst may besettled and the products fractionated.

The following example is introduced for the purpose of illustrating thetype'of results normally obtainable by the use of the process of theinvention although not with the intention of unduly restricting itsproper scope.

Normal pentane was placed in a pressure vessel and approximately 30% byweight of powdered 0 and substantially anhydrous zirconium chloride Thecomwas added. The pressure vessel was closed and an amount of hydrogenchloride introduced which corresponded to approximately 4% by, weight ofthe normal pentane. The pressure vessel was then heated for three hoursat approximately 150 C. and the products removed from the pressurevessel were then found to have the following composition:

Per cent Propane Iso-butane 41 n-Butane 19 i-Pentane i. 14 ,n-Pentane 3Higher hydrocarbons 3 carbon mixtures to the action of zirconiumchloride and hydrogen chloride.

4. A process for the isomerization of gasoline fractions containingsubstantial percentages of straight chain paraflin hydrocarbons whichcomprises subjecting said fractions to the action of zirconium chlorideand hydrogen chloride.

ARISTID v. GROSSE. HERMAN PINES.

